1. Field of the Invention
The present invention relates to a focusing torque control device for a lens barrel of a camera.
2. Description of the Related Art
Conventionally, a camera having an automatic focusing lens, which can be switched between an automatic focusing operation (hereinafter referred to as AF mode) and a manual focusing operation (hereinafter referred to as MF mode), is known. This automatic focusing lens is provided with a drive shaft which, in the AF mode, is connected to a motor housed in the camera body, moving a lens along the optical axis. In the MF mode, the drive shaft is disconnected from the motor so that the lens can be manually moved.
In such an automatic focusing lens, a focusing operation in the AF mode should be carried out at a high-speed, and the electric power consumption of the motor should be low. Therefore, a drive force for displacing the lens in the optical axis must be made minimal to ensure smooth movement of the lens.
However, if the drive force for displacing the lens along the optical axis is lowered, the lens can be moved along the optical axis by even a small force in the MF mode. Thus, the operability of a manual focusing operation is not good.